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<a name="boost.date_time.dst_calculator"></a><div class="titlepage"></div>
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<h2><span class="refentrytitle">Class template dst_calculator</span></h2>
<p>boost::date_time::dst_calculator — Dynamic class used to caluclate dst transition information. </p>
</div>
<h2 xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="refsynopsisdiv-title">Synopsis</h2>
<div xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="refsynopsisdiv"><pre class="synopsis"><span class="comment">// In header: &lt;<a class="link" href="../../date_time/doxy.html#header.boost.date_time.dst_rules_hpp" title="Header &lt;boost/date_time/dst_rules.hpp&gt;">boost/date_time/dst_rules.hpp</a>&gt;

</span><span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">typename</span> date_type_<span class="special">,</span> <span class="keyword">typename</span> time_duration_type_<span class="special">&gt;</span> 
<span class="keyword">class</span> <a class="link" href="dst_calculator.html" title="Class template dst_calculator">dst_calculator</a> <span class="special">{</span>
<span class="keyword">public</span><span class="special">:</span>
  <span class="comment">// types</span>
  <span class="keyword">typedef</span> <span class="identifier">time_duration_type_</span> <a name="boost.date_time.dst_calculator.time_duration_type"></a><span class="identifier">time_duration_type</span><span class="special">;</span>
  <span class="keyword">typedef</span> <span class="identifier">date_type_</span>          <a name="boost.date_time.dst_calculator.date_type"></a><span class="identifier">date_type</span><span class="special">;</span>         

  <span class="comment">// <a class="link" href="dst_calculator.html#id-1_3_14_15_3_23_2_1_2_5-bb">public static functions</a></span>
  <span class="keyword">static</span> <span class="identifier">time_is_dst_result</span> 
  <a class="link" href="dst_calculator.html#id-1_3_14_15_3_23_2_1_2_5_1-bb"><span class="identifier">process_local_dst_start_day</span></a><span class="special">(</span><span class="keyword">const</span> <span class="identifier">time_duration_type</span> <span class="special">&amp;</span><span class="special">,</span> <span class="keyword">unsigned</span> <span class="keyword">int</span><span class="special">,</span> <span class="keyword">long</span><span class="special">)</span><span class="special">;</span>
  <span class="keyword">static</span> <span class="identifier">time_is_dst_result</span> 
  <a class="link" href="dst_calculator.html#id-1_3_14_15_3_23_2_1_2_5_2-bb"><span class="identifier">process_local_dst_end_day</span></a><span class="special">(</span><span class="keyword">const</span> <span class="identifier">time_duration_type</span> <span class="special">&amp;</span><span class="special">,</span> <span class="keyword">unsigned</span> <span class="keyword">int</span><span class="special">,</span> <span class="keyword">long</span><span class="special">)</span><span class="special">;</span>
  <span class="keyword">static</span> <span class="identifier">time_is_dst_result</span> 
  <a class="link" href="dst_calculator.html#id-1_3_14_15_3_23_2_1_2_5_3-bb"><span class="identifier">local_is_dst</span></a><span class="special">(</span><span class="keyword">const</span> <span class="identifier">date_type</span> <span class="special">&amp;</span><span class="special">,</span> <span class="keyword">const</span> <span class="identifier">time_duration_type</span> <span class="special">&amp;</span><span class="special">,</span> 
               <span class="keyword">const</span> <span class="identifier">date_type</span> <span class="special">&amp;</span><span class="special">,</span> <span class="keyword">const</span> <span class="identifier">time_duration_type</span> <span class="special">&amp;</span><span class="special">,</span> 
               <span class="keyword">const</span> <span class="identifier">date_type</span> <span class="special">&amp;</span><span class="special">,</span> <span class="keyword">const</span> <span class="identifier">time_duration_type</span> <span class="special">&amp;</span><span class="special">,</span> 
               <span class="keyword">const</span> <span class="identifier">time_duration_type</span> <span class="special">&amp;</span><span class="special">)</span><span class="special">;</span>
  <span class="keyword">static</span> <span class="identifier">time_is_dst_result</span> 
  <a class="link" href="dst_calculator.html#id-1_3_14_15_3_23_2_1_2_5_4-bb"><span class="identifier">local_is_dst</span></a><span class="special">(</span><span class="keyword">const</span> <span class="identifier">date_type</span> <span class="special">&amp;</span><span class="special">,</span> <span class="keyword">const</span> <span class="identifier">time_duration_type</span> <span class="special">&amp;</span><span class="special">,</span> 
               <span class="keyword">const</span> <span class="identifier">date_type</span> <span class="special">&amp;</span><span class="special">,</span> <span class="keyword">unsigned</span> <span class="keyword">int</span><span class="special">,</span> <span class="keyword">const</span> <span class="identifier">date_type</span> <span class="special">&amp;</span><span class="special">,</span> 
               <span class="keyword">unsigned</span> <span class="keyword">int</span><span class="special">,</span> <span class="keyword">long</span><span class="special">)</span><span class="special">;</span>
<span class="special">}</span><span class="special">;</span></pre></div>
<div class="refsect1">
<a name="id-1.3.14.15.3.23.5.4"></a><h2>Description</h2>
<div class="refsect2">
<a name="id-1.3.14.15.3.23.5.4.2"></a><h3>
<a name="id-1_3_14_15_3_23_2_1_2_5-bb"></a><code class="computeroutput">dst_calculator</code> public static functions</h3>
<div class="orderedlist"><ol class="orderedlist" type="1">
<li class="listitem">
<pre class="literallayout"><span class="keyword">static</span> <span class="identifier">time_is_dst_result</span> 
<a name="id-1_3_14_15_3_23_2_1_2_5_1-bb"></a><span class="identifier">process_local_dst_start_day</span><span class="special">(</span><span class="keyword">const</span> <span class="identifier">time_duration_type</span> <span class="special">&amp;</span> time_of_day<span class="special">,</span> 
                            <span class="keyword">unsigned</span> <span class="keyword">int</span> dst_start_offset_minutes<span class="special">,</span> 
                            <span class="keyword">long</span> dst_length_minutes<span class="special">)</span><span class="special">;</span></pre>Check the local time offset when on dst start day. <p>On this dst transition, the time label between the transition boundary and the boudary + the offset are invalid times. If before the boundary then still not in dst. 

</p>
<div class="variablelist"><table border="0" class="variablelist compact">
<colgroup>
<col align="left" valign="top">
<col>
</colgroup>
<tbody><tr>
<td><p><span class="term">Parameters:</span></p></td>
<td><div class="variablelist"><table border="0" class="variablelist compact">
<colgroup>
<col align="left" valign="top">
<col>
</colgroup>
<tbody>
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<td><p><span class="term"><code class="computeroutput">dst_length_minutes</code></span></p></td>
<td><p>Number of minutes to adjust clock forward </p></td>
</tr>
<tr>
<td><p><span class="term"><code class="computeroutput">dst_start_offset_minutes</code></span></p></td>
<td><p>Local day offset for start of dst </p></td>
</tr>
<tr>
<td><p><span class="term"><code class="computeroutput">time_of_day</code></span></p></td>
<td><p>Time offset in the day for the local time </p></td>
</tr>
</tbody>
</table></div></td>
</tr></tbody>
</table></div>
</li>
<li class="listitem">
<pre class="literallayout"><span class="keyword">static</span> <span class="identifier">time_is_dst_result</span> 
<a name="id-1_3_14_15_3_23_2_1_2_5_2-bb"></a><span class="identifier">process_local_dst_end_day</span><span class="special">(</span><span class="keyword">const</span> <span class="identifier">time_duration_type</span> <span class="special">&amp;</span> time_of_day<span class="special">,</span> 
                          <span class="keyword">unsigned</span> <span class="keyword">int</span> dst_end_offset_minutes<span class="special">,</span> 
                          <span class="keyword">long</span> dst_length_minutes<span class="special">)</span><span class="special">;</span></pre>Check the local time offset when on the last day of dst. <p>This is the calculation for the DST end day. On that day times prior to the conversion time - dst_length (1 am in US) are still in dst. Times between the above and the switch time are ambiguous. Times after the start_offset are not in dst. 

</p>
<div class="variablelist"><table border="0" class="variablelist compact">
<colgroup>
<col align="left" valign="top">
<col>
</colgroup>
<tbody><tr>
<td><p><span class="term">Parameters:</span></p></td>
<td><div class="variablelist"><table border="0" class="variablelist compact">
<colgroup>
<col align="left" valign="top">
<col>
</colgroup>
<tbody>
<tr>
<td><p><span class="term"><code class="computeroutput">dst_end_offset_minutes</code></span></p></td>
<td><p>Local time of day for end of dst </p></td>
</tr>
<tr>
<td><p><span class="term"><code class="computeroutput">time_of_day</code></span></p></td>
<td><p>Time offset in the day for the local time </p></td>
</tr>
</tbody>
</table></div></td>
</tr></tbody>
</table></div>
</li>
<li class="listitem">
<pre class="literallayout"><span class="keyword">static</span> <span class="identifier">time_is_dst_result</span> 
<a name="id-1_3_14_15_3_23_2_1_2_5_3-bb"></a><span class="identifier">local_is_dst</span><span class="special">(</span><span class="keyword">const</span> <span class="identifier">date_type</span> <span class="special">&amp;</span> current_day<span class="special">,</span> 
             <span class="keyword">const</span> <span class="identifier">time_duration_type</span> <span class="special">&amp;</span> time_of_day<span class="special">,</span> 
             <span class="keyword">const</span> <span class="identifier">date_type</span> <span class="special">&amp;</span> dst_start_day<span class="special">,</span> 
             <span class="keyword">const</span> <span class="identifier">time_duration_type</span> <span class="special">&amp;</span> dst_start_offset<span class="special">,</span> 
             <span class="keyword">const</span> <span class="identifier">date_type</span> <span class="special">&amp;</span> dst_end_day<span class="special">,</span> 
             <span class="keyword">const</span> <span class="identifier">time_duration_type</span> <span class="special">&amp;</span> dst_end_offset<span class="special">,</span> 
             <span class="keyword">const</span> <span class="identifier">time_duration_type</span> <span class="special">&amp;</span> dst_length<span class="special">)</span><span class="special">;</span></pre>Calculates if the given local time is dst or not. <p>Determines if the time is really in DST or not. Also checks for invalid and ambiguous. 

</p>
<div class="variablelist"><table border="0" class="variablelist compact">
<colgroup>
<col align="left" valign="top">
<col>
</colgroup>
<tbody><tr>
<td><p><span class="term">Parameters:</span></p></td>
<td><div class="variablelist"><table border="0" class="variablelist compact">
<colgroup>
<col align="left" valign="top">
<col>
</colgroup>
<tbody>
<tr>
<td><p><span class="term"><code class="computeroutput">current_day</code></span></p></td>
<td><p>The day to check for dst </p></td>
</tr>
<tr>
<td><p><span class="term"><code class="computeroutput">dst_end_day</code></span></p></td>
<td><p>Ending day of dst for the given locality </p></td>
</tr>
<tr>
<td><p><span class="term"><code class="computeroutput">dst_end_offset</code></span></p></td>
<td><p>Time offset within day given in dst for dst boundary </p></td>
</tr>
<tr>
<td><p><span class="term"><code class="computeroutput">dst_start_day</code></span></p></td>
<td><p>Starting day of dst for the given locality </p></td>
</tr>
<tr>
<td><p><span class="term"><code class="computeroutput">dst_start_offset</code></span></p></td>
<td><p>Time offset within day for dst boundary </p></td>
</tr>
<tr>
<td><p><span class="term"><code class="computeroutput">time_of_day</code></span></p></td>
<td><p>Time offset within the day to check </p></td>
</tr>
</tbody>
</table></div></td>
</tr></tbody>
</table></div>
</li>
<li class="listitem">
<pre class="literallayout"><span class="keyword">static</span> <span class="identifier">time_is_dst_result</span> 
<a name="id-1_3_14_15_3_23_2_1_2_5_4-bb"></a><span class="identifier">local_is_dst</span><span class="special">(</span><span class="keyword">const</span> <span class="identifier">date_type</span> <span class="special">&amp;</span> current_day<span class="special">,</span> 
             <span class="keyword">const</span> <span class="identifier">time_duration_type</span> <span class="special">&amp;</span> time_of_day<span class="special">,</span> 
             <span class="keyword">const</span> <span class="identifier">date_type</span> <span class="special">&amp;</span> dst_start_day<span class="special">,</span> 
             <span class="keyword">unsigned</span> <span class="keyword">int</span> dst_start_offset_minutes<span class="special">,</span> 
             <span class="keyword">const</span> <span class="identifier">date_type</span> <span class="special">&amp;</span> dst_end_day<span class="special">,</span> 
             <span class="keyword">unsigned</span> <span class="keyword">int</span> dst_end_offset_minutes<span class="special">,</span> <span class="keyword">long</span> dst_length_minutes<span class="special">)</span><span class="special">;</span></pre>Calculates if the given local time is dst or not. <p>Determines if the time is really in DST or not. Also checks for invalid and ambiguous. 

</p>
<div class="variablelist"><table border="0" class="variablelist compact">
<colgroup>
<col align="left" valign="top">
<col>
</colgroup>
<tbody><tr>
<td><p><span class="term">Parameters:</span></p></td>
<td><div class="variablelist"><table border="0" class="variablelist compact">
<colgroup>
<col align="left" valign="top">
<col>
</colgroup>
<tbody>
<tr>
<td><p><span class="term"><code class="computeroutput">current_day</code></span></p></td>
<td><p>The day to check for dst </p></td>
</tr>
<tr>
<td><p><span class="term"><code class="computeroutput">dst_end_day</code></span></p></td>
<td><p>Ending day of dst for the given locality </p></td>
</tr>
<tr>
<td><p><span class="term"><code class="computeroutput">dst_end_offset_minutes</code></span></p></td>
<td><p>Offset within day given in dst for dst boundary (eg 120 for US which is 02:00:00) </p></td>
</tr>
<tr>
<td><p><span class="term"><code class="computeroutput">dst_length_minutes</code></span></p></td>
<td><p>Length of dst adjusment (eg: 60 for US) </p></td>
</tr>
<tr>
<td><p><span class="term"><code class="computeroutput">dst_start_day</code></span></p></td>
<td><p>Starting day of dst for the given locality </p></td>
</tr>
<tr>
<td><p><span class="term"><code class="computeroutput">dst_start_offset_minutes</code></span></p></td>
<td><p>Offset within day for dst boundary (eg 120 for US which is 02:00:00) </p></td>
</tr>
<tr>
<td><p><span class="term"><code class="computeroutput">time_of_day</code></span></p></td>
<td><p>Time offset within the day to check </p></td>
</tr>
</tbody>
</table></div></td>
</tr></tbody>
</table></div>
</li>
</ol></div>
</div>
</div>
</div>
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<td align="right"><div class="copyright-footer">Copyright © 2001-2005 CrystalClear Software, Inc<p>Subject to the Boost Software License, Version 1.0. (See accompanying file
    <code class="filename">LICENSE_1_0.txt</code> or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)</p>
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